diff --git a/uppsrc/Core/Heap.h b/uppsrc/Core/Heap.h
index 98ab8c898..e7d34f62d 100644
--- a/uppsrc/Core/Heap.h
+++ b/uppsrc/Core/Heap.h
@@ -20,7 +20,7 @@ void *MemoryAlloc48();
 void  MemoryFree48(void *ptr);
 void  MemoryFreeThread();
 void  MemoryCheck();
-void  MemoryDump();
+void  MemoryDumpLarge();
 void  MemoryDumpHuge();
 int   MemoryUsedKb();
 int   MemoryUsedKbMax();
diff --git a/uppsrc/Core/HeapImp.h b/uppsrc/Core/HeapImp.h
index 84e6b48b9..e37045a30 100644
--- a/uppsrc/Core/HeapImp.h
+++ b/uppsrc/Core/HeapImp.h
@@ -265,7 +265,6 @@ struct Heap : BlkHeap<HugeHeapDetail, 4096> {
 	enum {
 		LUNIT = 256, // granularity of large blocks (size always a multiple of this)
 		LPAGE = LUNIT - 1, // number of LUNITs in large page
-		LCVCOUNT = 9, // SignificantBits(LPAGE) + 1
 		LOFFSET = 64, // offset from 64KB start to the first block header
 
 		NKLASS = 23, // number of small size classes
@@ -318,13 +317,8 @@ struct Heap : BlkHeap<HugeHeapDetail, 4096> {
 	};
 	
 	struct LargeHeapDetail {
-		BlkHeader_<LUNIT> freelist[LCVCOUNT][1];
-		static int Cv(int n) { return SignificantBits(n); }
-
-		void Free64KB(BlkHeader_<LUNIT> *h);
-		void LinkFree(BlkHeader_<LUNIT> *h) {
-			Dbl_LinkAfter(h, freelist[Cv(h->GetSize())]);
-		}
+		BlkHeader_<LUNIT> freelist[25][1];
+		void LinkFree(BlkHeader_<LUNIT> *h);
 	};
 	
 	struct LargeHeap : BlkHeap<LargeHeapDetail, LUNIT> {};
@@ -348,6 +342,10 @@ struct Heap : BlkHeap<HugeHeapDetail, 4096> {
 		LargeHeap::BlkHeader *GetFirst()   { return (LargeHeap::BlkHeader *)((byte *)this + LOFFSET); } // pointer to data area
 	};
 
+	static int lclass[];
+	static int free_lclass[255];
+	static int alloc_lclass[255];
+
 	static_assert(sizeof(BlkPrefix) == 16, "Wrong sizeof(BlkPrefix)");
 	static_assert(sizeof(DLink) == 64, "Wrong sizeof(DLink)");
 	
@@ -436,7 +434,7 @@ struct Heap : BlkHeap<HugeHeapDetail, 4096> {
 	size_t LGetBlockSize(void *ptr);
 
 	void   Make(MemoryProfile& f);
-	void   Dump();
+	void   DumpLarge();
 	void   DumpHuge();
 
 	static void Shrink();
diff --git a/uppsrc/Core/heaputil.cpp b/uppsrc/Core/heaputil.cpp
index fbd9a37a6..28610a990 100644
--- a/uppsrc/Core/heaputil.cpp
+++ b/uppsrc/Core/heaputil.cpp
@@ -181,33 +181,25 @@ void Heap::Make(MemoryProfile& f)
 	}
 }
 
-void Heap::Dump()
+void Heap::DumpLarge()
 {
 	Mutex::Lock __(mutex);
 	DLink *m = large->next;
+	auto& out = VppLog();
 	while(m != large) {
 		LargeHeap::BlkHeader *h = m->GetFirst();
-		RLOG("--------------------------");
+		out << h << ": ";
 		for(;;) {
-			RLOG(asString(h) << " " << h->GetSize() << (h->IsFree() ? " FREE" : ""));
+			if(h->IsFree())
+				out << "#";
+			out << h->GetSize() * 0.25 << ' ';
 			if(h->IsLast())
 				break;
 			h = h->GetNextHeader();
 		}
+		out << "\r\n";
 		m = m->next;
 	}
-	HugePage *pg = huge_pages;
-	while(pg) {
-		BlkPrefix *h = (BlkPrefix *)pg->page;
-		RLOG("==========================");
-		for(;;) {
-			RLOG(asString(h) << " " << h->GetSize() << (h->IsFree() ? " FREE" : ""));
-			if(h->IsLast())
-				break;
-			h = h->GetNextHeader(4096);
-		}
-		pg = pg->next;
-	}
 }
 
 void Heap::DumpHuge()
diff --git a/uppsrc/Core/lheap.cpp b/uppsrc/Core/lheap.cpp
index 2f4a9e767..a8f1841eb 100644
--- a/uppsrc/Core/lheap.cpp
+++ b/uppsrc/Core/lheap.cpp
@@ -11,8 +11,31 @@ namespace Upp {
 
 #include "HeapImp.h"
 
+int Heap::lclass[] = { 0, 4, 5, 6, 7, 8, 9, 11, 13, 15, 18, 22, 27, 33, 40, 49, 60, 73, 89, 109, 134, 164, 201, 225, 255 };
+int Heap::free_lclass[255]; // free block size -> lclass, size is >= class sz
+int Heap::alloc_lclass[255]; // allocation size -> lclass, size <= class sz
+
+
+void Heap::LargeHeapDetail::LinkFree(BlkHeader_<LUNIT> *h)
+{
+	Dbl_LinkAfter(h, freelist[free_lclass[h->GetSize()]]);
+}
+
 void Heap::LInit()
 {
+	ASSERT(__countof(lheap.freelist) == __countof(lclass));
+	ONCELOCK {
+		int ai = 0;
+		int fi = 0;
+		for(int i = 0; i <= 255; i++) {
+			if(i > lclass[ai])
+				ai++;
+			if(i >= lclass[fi + 1])
+				fi++;
+			alloc_lclass[i] = ai;
+			free_lclass[i] = fi;
+		}
+	}
 	for(int i = 0; i <= __countof(lheap.freelist); i++)
 		Dbl_Self(lheap.freelist[i]);
 	big->LinkSelf();
@@ -31,6 +54,10 @@ void *Heap::TryLAlloc(int i0, word wcount)
 				return (BlkPrefix *)h + 1;
 			}
 			h = h->next;
+			RHITCOUNT("next");
+			static int q = 0;
+			if(++q < 1000)
+				RLOG(asString(sz) << " " << asString(wcount));
 		}
 	}
 	return NULL;
@@ -76,7 +103,7 @@ void *Heap::LAlloc(size_t& size)
 #endif
 
 	size = ((int)wcount * LUNIT) - sizeof(BlkPrefix);
-	int i0 = lheap.Cv(wcount);
+	int i0 = alloc_lclass[wcount];
 
 	if(large_remote_list)  // there might be blocks of this heap freed in other threads
 		LargeFreeRemote(); // free them first
diff --git a/uppsrc/Core/sheap.cpp b/uppsrc/Core/sheap.cpp
index 5fe65fc73..c4afdc0ed 100644
--- a/uppsrc/Core/sheap.cpp
+++ b/uppsrc/Core/sheap.cpp
@@ -429,9 +429,9 @@ MemoryProfile::MemoryProfile()
 	ThreadHeap()->Make(*this);
 }
 
-void MemoryDump()
+void MemoryDumpLarge()
 {
-	ThreadHeap()->Dump();
+	ThreadHeap()->DumpLarge();
 }
 
 void MemoryDumpHuge()